Fatigue growth of short cracks in Ti-17: experiments and simulations
2007 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 74, no 15, 2293-2310 p.Article in journal (Refereed) Published
The fatigue behaviour of through thickness short cracks was investigated in Ti-17. Experiments were performed on a symmetric four-point bend set-up. An initial through thickness crack was produced by cyclic compressive load on a sharp notch. The notch and part of the crack were removed leaving an approximately 50 mu m short crack. The short crack was subjected to fatigue loading in tension. The experiments were conducted in load control with constant force amplitude and mean values. Fatigue growth of the short cracks was monitored with direct current potential drop measurements. Fatigue growth continued at constant R-ratio into the long crack regime. It was found that linear elastic fracture mechanics (LEFM) was applicable if closure-free long crack growth data from constant K-1max test were used. Then, the standard Paris' relation provided an upper bound for the growth rates of both short and long crack.The short crack experiments were numerically reproduced in two ways by finite element computations. The first analysis type comprised all three phases of the experimental procedure: precracking, notch removal and fatigue growth. The second analysis type only reproduced the growth of short cracks during fatigue loading in tension. In both cases the material model was elastic-plastic with combined isotropic and kinematic hardening. The agreement between crack tip opening displacement range, cyclic J-integral and cyclic plastic zone at the crack tip with Delta K-1 verified that LEFM could be extended to the present short cracks in Ti-17. Also, the crack size limits described in the literature for LEFM with regards to plastic zone size hold for the present short cracks and cyclic softening material.
Place, publisher, year, edition, pages
2007. Vol. 74, no 15, 2293-2310 p.
short crack, fatigue crack growth, potential drop method, titanium alloy, crack closure
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-6423DOI: 10.1016/j.engfracmech.2006.11.016ISI: 000247823000001ScopusID: 2-s2.0-34249659123OAI: oai:DiVA.org:kth-6423DiVA: diva2:11128
QC 201008272006-11-232006-11-232011-11-07Bibliographically approved